A known oil cooling system for a motor is disclosed in JPH08 (1996)-130856A. According to the known oil cooling system for the motor disclosed in JPH08 (1996)-130856A, an oil discharging portion for cooling coils is positioned above an coil end, and the coils positioned at an upper portion of the motor is cooled by the oil discharged with pressure through the oil discharging portion positioned at the upper portion of the motor towards the coil end positioned at a lower level relative to the oil discharging portion in a radial direction of the motor.
According to the construction of the known oil cooling system for the motor disclosed in JPH08 (1996)-130856A, because the oil discharging portion is positioned at the upper portion of the motor, the oil is not sprayed on or applied to the coils provided at a bottom portion of the motor. Because the coils, on which the oil is not sprayed on or applied to, is not cooled by the oil, the temperature thereof increases compared to the coil to which the oil is applied. In order to control the temperature of a motor, it is necessary to limit the temperature of the coil having the highest temperature. Thus, according to the construction of the known oil cooling system for the motor disclosed in JPH08 (1996)-130856A, a thermal rating is not improved and a size of the motor is increased.
A need thus exists for an oil cooling system for a motor which is not susceptible to the drawback mentioned above.